As described in Patent Literature 1, an absorbent body with a desired shape is formed in such a way that, a mixed flow is formed by carrying fluff pulp formed by crushing a pulp sheet on an air flow to a duct and at the same time supplying a water absorbing polymer in the duct to be merged with the fluff pulp carrying flow, and the mixed flow is then transported to a rotating fiber stacking drum so that the mixed flow is adsorbed and retained by an adsorbent molding section which is formed on the outer circumference of the rotating fiber stacking drum. The adsorption to the adsorbent molding section is performed in such a way that the air in the rotating fiber stacking drum is sucked by a sucking means connected to a side wall of the rotating fiber stacking drum to keep the inside of the rotating fiber stacking drum to be negative in pressure.